Control system and apparatus



Nov. 3,1936. H. F. -PARKER 2,059,271

CONTROL SYSTEM AND APPARATUS Filed May 13, "1933 3 Sheets-Sheet l ATTORNEY H. F. PARKER CONTROL SYSTEM AND APPARATUS Nov. 3, 1936.

Filed May 15, 1953 3 Sheets-Sheet 2 lNvENToR ATTORNEY Nov. 3, 1936. H. F: PARKER 2,059,271

CONTROL SYSTEM AND APPARATUS Filed May 13, 1953 I 5 Sheets-Sheet 3 ATTORNEY BVM/6,5

INV NTOR f Patented Nov. 3, '-1936 UNITED STATES PATENT OFFICE CONTRGL SYSTEM AND APPARATUS Humphrey F. Parker, New York, N. Y.

Application May 13, 1933, Serial No. 670,855

26 Claims. (Cl-l'I--Zl' This invention relates to control systems and with particularity to an improved form of automatic control system'.

The invention has for its principal object to provide a novel form of control, suitable for use in automatic steering, orin any field where the heading and/or position of an object areto be indicated and/or controlled.

Another object of the invention relates to a heading and/or position indicator or` the like, which has a. maximum sensitivity and accuracy. In carrying out this object of the invention it is proposed to employ an extremely sensitive movable master control device -which exercises its control without physical contact with `the devicesA to be controlled.

Another object of the invention relates to a heading and/or position indicator or the like in which a member, receiving electrical impulses from a relatively movable point, uses such impulses to transmit signals to another relatively movable point without physical contact between the various parts ofthe system.

Another object of the invention resides in an improved form of master control device which is capable of controlling, with maximum accuracy. one or more repeater devices, such as position indicators, clocks, compasses, etc.

Another object is to provide a novel mechanism for controlling follow-up devices such as employed in automatic steering systems or the like.

A feature of the invention relates to an improved form of master compass.

Another `feature relates to the novel Vmechanism for controlling the heading or direction of a moving craft.

A further feature relates to a novel method of electrically coupling a master compass, a direction indicator, or similar device to a repeating system.

A still further feature relates to a simple, ac-

, curate and reliable'master control device which operates by space induction to control one or more repeaters.

Other features and advantages not specifically enumerated will be apparent after a consideration Fig. 2 is a partial sectional view of Fig. 1, taken along the line 2--2 thereof;

Fig. 3 is an enlarged detailed sectional view of one of the compass supports and the mechanism for rotating said supports taken on the line 3-3 5 of Fig. 1;

Fig. 4 is a detailed enlarged view of certain of the control mechanism of the compass taken on the line 4-4 of Fig. 1; v

Fig. 5 is a schematic diagram explanatory of 10 certain features of the invention; l

Fig. 6 is a detailed schematic diagram of a preferred form of electrical system for carrying out the invention;

Fig. 'l is a detailed schematic diagram of a pre- 15 ferred form of electrical system for the follow-up mechanism for controlling the heading of a ship or other craft;

Fig. 8 is a detailedschematic diagram of oneV manner of controlling\the rudder or other direc- 20 tion control device of a ship or other craft;

Fig. 9 shows how the steering system according to the invention may operate either under manual control or automatic control:

Fig. 10 is a detailedview of certain of the mech- 25 anism of Fig. 9; and

Fig. 11 is a schematic diagram of a modification of part of the system shown in Fig. 7.

Referring more particularly to Figs. 1 and 2, there is shown a preferred type of master control '30 device in the compass that may be used in carrying out the invention. This compass consists of a group of permanent magnets formed of a number of magnetized hardened steel needles packed together and sealed in tubes i of brass or other 35 non-,magnetic material andwith all the northseeking poles facing the sameway within the tubes. The tubes i are fastened in any suitable manner, for example by soldering, to a hollow float 2 of non-magnetic material such as brass 4o or other metal, the shape and size of the iloat being preferably such asy to provide sufllcient buoyancy to allow the iloat and magnet assembly to barely sinkin the liquid lwithin the bowl I. The liquid l is preferably a non-conductor in the 45 form of a non-viscous transparent ollsuch as a light transformer oil or the like.

As shown in the drawings, the noat comprises a substantially hemispherical portion 5 and a disc portion 0. 'I'he float assembly also carries 50 a compass card 1 of mica or other similar material, the upper surface of which is provided with the usual compass markings or other directional markings.

Centrally carriedby the oatportion l is a II which in turn is fastened to the .flanged rim I2 of the bowl by suitable screws I8.

Bowl 4 is provided with trunnions I4 which rest in trunnion bearings I5 in gimbal ring I8. Ring I8 isin turn provided with diametrically disposed trunnions I1 located on a diameter normal to that on which the trunnions I4 are 1ocated. Trunnions I1, instead of being supported in the usual fixed binnacle, are, as shown lin Figs. l and 3, provided with bearings I8 carried in a rotatable ring I9 for purposes described hereinbelow. The Wall of bowl 4 is provided with a reference or lubber line 2D, the relationship of which with respect to the markings on the compass card 1, indicates the heading of the ship or other craft in which the device is installed. In other words, the compass card, apart from parasitic disturbances, remains in fixed azimuth by reason of the natural attraction between the earths magnet and the compass needles, while the lubber line 20 being fast to the ship, moves in relation to the card 'I as the shipsr direction is changed.

One of the important practical features of this invention is the mechanism for maintaining the lubber line 2|! in alignment or in any other fixed relation with a selected marking on the compass card. For this purpose it is necessary to provide follow-up mechanism by means of which an incipient departure of the compass support from its preselected normal or neutral position,

causes the said support to reass'ume its normal or neutral position. This follow-up motion may be provided by a suitable reversible motor which may be controlled as to direction and duration of rotation by electrical signals controlled by the compass. Various methods of producing and utilizing these signals have been proposed heretofore, probably the simplest being a contact arm carried by the compass float, current being provided to this arm through the compass pivot. A pair of fixed contacts are then disposed at either side of the lubber line. When the fioat contact arm is midway between the fixed contacts, the follow-up mot'r will not act to vary the position of the compass bowl or support. A departure would, however, cause the float contact to engage physically one or the other of the fixed contacts, depending on the direction of the departure, resulting in corresponding rotation of the follow-up motor. Thls arrangement has the very serious disadvantage that the directive force exerted on the fioat by the earths magnetic field is so small as to be incapable of physically closing a contact with any degree of reliability or uniformity. In addition, the passage of the control current throughthe pivot tends to electrolyze and eventually destroy the pivot point. It has been proposed heretofore to employ a liquid electrolyte and to rely upon the variations of resistance between the fixed and movable contacts resulting from a departure, but -here again unless extreme precautions are taken, the eletrolyte in time deteriorates the contacts and changes their resistance. The resistance of the electrolyte itself may also change because of its contact with various metal parts within the bowl. The above disadvantages are overcome and a thoroughly reliable and accurate instrument is provided in accordance with the present invention by eliminating any physical or rubbing connection between the fixed and movable contacts, or without relying upon variations of resistance of the electrolytic bath or the like.

In accordance with this particular phase of the invention, the control signals are transferred from the fixed to the movable parts of the compass solely by space induction, electrostatic induction, or electromagnetic induction, or a combination of electrostatic and electromagnetic induction.

In order to complete the control circuits, the plate glass cover lll carries five terminals or binding posts 2|, 22, 22, 28, 28. carries at its lower end a hemispherically shaped metal member 24 preferably of brass or other non-magnetic material; The member 24 is preferably so disposed that the center of its spherical curvature lies as closely as possible at the point of the pivot 9. Since, as above described, the float section 5 is also hemispherlcal, there is a uniform spacing between the member 24 and the float section 5. Consequently, any electric potential impressed upon the member 24 produces uniform electrostatic fields between the said members and the lines of force are symmetrical with respect to the pivot point 8. Since the liquid 8 is preferably a nonfconductor, members 24 and 5 constitute in effect a condenser. Consequently, if a potential is impressed upon the member 24 a corresponding potential will be electrostatically induced upon the member 8, the induced potential being a function of the opposed areas between the members 5 and 24 and the dielectric constant of the liquid 8. The posts 22 and 28 carry a semi-circular metal ring 2l, and a similar semi-circular metal ring 28 is carried by the posts 22* and 28. As shown more clearly in Fig. 1, the rings 25 and 28 are spaced apart at their opposing ends. Preferably, each of the rings 25, 28 is formed to the shape of a spherical sector and the rings are disposed concentrically w h relation to the pivot 8. The float portion 8 has attached thereto a metallic arm 21 which terminates in a plate 2l conforming in curvature to the Lcurvature of the rings 25 and 28 so as to be uniformly spaced therefrom at all points. As indicated-clearly in Fig.

2 of the drawings, each of the posts 2l, 22, 22e, 23, 28, is rigidly held in position in the glass, top I0 by a bushing 29! and nut 80.. With this arrangement therefore, the members 5,24, 28, 28, 28 are symmetrically and/or concentrically mounted with relation to the pivot 8. With the above described arrangement, therefore, the compass float may move in planes at an angle to the normal plane of the compass rotation without disturbing the properoperation of the system, since such movements do not change the radial spacing between the members 2l, 28 and 28.

Normally, the member 281s in registry with the gap 28 between the ends of the ring members 2l and 28 with an equal extent of overlap between the said member 28 and the ends of the rings. Consequently, if a potential is impressed upon the member 24, corresponding potentials of equal magnitude are induced upon the rings 25 and 28, resulting from the fact that the member 2l forms with the said rings a pair of variable condensers, the member 28 being the movable plate and the members 2iland 28 being the fixed plates. If,.

The post 2k 4 rings to a greater extent than the other",V their:

unequal potentials wm be induced in the and i acteert This differential potential may then be utilized,

ferential potential is controlled by the compass' float and this differential potential may be taken off the binding posts 22, 22a or 23, 23 without any physical contact between the compass float and the stationary collector` rings 25, 26.

Referring to Fig. 5 there is shown, for explanatory purposes, an electrical circuit that may be used in conjunction with the deviceof Figs. 1 and 2. In Fig. 5, if an alternating current of suitable frequency is applied to the primary winding 3| of a step--up transformer, an electromotiveforce of high potential but low power is induced lin the secondary winding 32. The secondary winding 32 has its ends connected across the points 33 and y 34 of an alternating current balancing network,

this connection being preferably effected through a condenser 35 of fixed capacity. The two upper arms of the balancing network are formed of the variable condensers v36, 31, while the two lower arms of the network are composed' of the windings 38. 39 of the auto-transformer 40. If the windings 38 and 39 are electrically balanced, then for a given potential impressed at the point 3.3, the resultant E. M. F. across the total windings 38 and 39 will be zero provided the capacities 36, 31 are of equal magnitude. If, on the other hand, one of the capacities 36 or 31 is increased in magnitude or the other capacity is decreased, then the opposing E. M. F.s induced in the windings 38 and 38 will be unequal and a measurable differential E. M. F. will be developed across the total winding of the transformer 48. By means of a suitable electron discharge amplifier 4l)a this differential E. M. F. is amplified and used to control the follow-up motor in the manner described l hereinbelow.

For example, Fig. 5 shows schematically one manner of employing the amplified E. M. F.s to control the direction of rotation of a reversible motor having an armature |5|. As indicated in this drawing, the currents in the secondary winding |52 are applied across a pair of devices |53, |54. These latter devices are preferably of the type which pass current or relay current only for a given polarity of potential impressed thereon. For example, they may take the form of oppositely poled vacuum tubes, so-called Thyratrcns, or

4even oppositely poled rectifiersl The outputs of these devices |53, |54 are connected to'the field windings |55,V |56 associated with the armature |5I. Aslschematically illustrated in Fig. 5, the devices |53, |54 are of the three-electrode type,

each having an emitter cathode |51, a control electrode |58 and an anode |59. The anode or output current may be supplied from a suitable y source such as an alternator |60 in series with the armature |5| and thence through the field windings |55, |56 in the manner well understood in the vacuum tube or Thyratron art. For a given polarity of current in the secondary winding |52 the device. |53, for example, will allow current to pass through the field winding |55, whereas for a current of the opposite polarity in the winding |52, the device |54 functions to allow current to flow through the field winding |56. By means of the separate windings |55, |56 therefore, the direction of rotation of the armature |5| may be controlled.

Referring to Fig. 6, there is shown a complete the primary winding 43 of a step-up transformer.

The high potential end ofthe transformer sec ondary 44 is connected to the member 24 coru responding to the member 24 of Figs. 1 and 2. Preferably, the low potential end of the secondary Winding may be grounded as shown and, if desired, a condenser 45 may be connected across this winding. The arm 28 of the device of Fig. 2 is represented by the same numeral in Fig. 6, and the collector rings 25, 26 are likewise desigfl nated by the same numerals in Fig. 6. Preferably, the transformer isdesigned to produce ar relatively high voltage in the secondary, for example, of the order of r2000 v. The collector rings 25 and 26 are connected across the winding sections 46 and 41 of' an auto-transformer 48 corresponding tothe transformer 48 of Fig. 5. Preferably, thel auto-transformer 48 is shunted by a condenser 49 for tuning the amplifier to the frequency of the current from terminals 4| and 42 and also for increasing the input impedance to the amplifier tube 50. The tube 58 may consist of any wellknown form of electron discharge stood that the system is entirely operative without employing tunedampliers. The amplified output is delivered to the terminals 58 and 59 whence it may be utilized to drive any suitable form of follow-up control mechanism. Thus as illustrated in Fig. 6, the follow-up control mechanism comprises a dynamometer 68 having one of its coils 6| connected across the line terminals 4|, 42 and its other coil 62 connected across the amplifier terminals 58 and 53. The direction of torque developed in the dynamometer 60 will then be a function of the direction 'of current flow of the amplied output acrossterminals 58 and 59. This direction is in turn dependent upon the position of the movable member 28 with respect to the collector rings 25 and 26. In other words, if the member 28 is symmetrically disposed with relation to the rings 25 and 26 so as to overlap them equally, there will be no differential E. M. F. produced across the transformer 48 and consequently the dynamometer shaft will remain in its neutral or normal position. On the other hand, should the member 28 move towards the ring 25 and away from the ring 26, there will be produced a differential E. M. F. which, upon being amplified, will cause the rotation of the dynamometer shaft in one direction. If, however, the member 28 should move towards the ring 26 and 4away from the ring 25, then the dynamometer shaft will'rotate in the opposite direction.

As described hereinabove, the alternating potential developed in the secondary winding 44 induces corresponding potentials on the member 5 and on the members 25 and 26, the magnitude of the induced charges on these latter two mem- In Fig. 6 a suitable source I bers being determined by the movable member 28, which in turn is controlled by the position of the compass, it being directly connected thereto as described above in connection with Figs. 1 and 2.

It is assumed that the phases of the currents in the dynamometer coils Ii or 62 are either the same or are displaced 180 apart, and in order to achieve this condition suitable phase correcting means or circuits may be employed in the ampliiler itself or between the amplifier and the dynamometer. From the description given above in connection with Fig. 2, it will be noted that since the compass float assembly is supported by a jewelied bearing 8, this assembly is electrically insulated from ground and from the bowl l. However, if desired, additional screening or electrostatic guard-rings" may be employed to prevent parasitic disturbances from affecting the needle and from affecting the induced potentials on the rings 25 and 25. The system of Fig. 6, therefore, provides an arrangement whereby the movements of the compass needle cause the production of corresponding dierentlal E. M. Fis which are amplified, and the polarity of the differential E. M. F.s is utilized to control the direction of rotation of the follow-up control dynamometer.

It will be understood, of course, that the invention is not limited to any particular frequency of alternating current and, as a matter of fact, a source of direct current may be connected to the terminal 2i, providing suitable resistance leaks are incorporated for leaking off the charge from the rings 25 and 2i at a predetermined rate. It the line current is a direct current then, if desired, a suitable form of D. C.A. C. converter may be employed between the line and the terminal 2l. It will be understood, of course, that if a sufiiciently high-powered amplifier is employed, the dynamometer il may be replaced by any well-known form of reversibleA motor which begins to rotate only when current flows across the terminals Si and 59. For example, the dynamometer 60 may be replaced by a series type A. C. motor which has its amature fed with current from the terminals li and 42 through a resistance or impedance. Such a motor will rotate only when the field is energized from the amplifier terminals il and i9 and then only in the direction determined by the phase of the amplined voltage, which in turn is controlled by the angular displacement of the compass needle. Preferably, however, when the system of Fig. 6 is to be used for controlling the compass bowl 4 or other device, the shaft of the dynamometer 6l may be utilized to close selectively suitable relay contacts which in turn control the supply of current to the coils of a reversible motor or areversible clutch in conjunction with a continuously running motor.

As explained hereinabove, the compass float, except for parasitic disturbanceaalways remains fixed in azimuth, but its support, including the bowl I, moves according to the yawing of the ship, and suitable follow-up mechanism may act upon an incipient movement of the bowl or sup-I port to restore it to its normal or neutral relationship with respect to the float. Thus the shaft or rotor of the dynamometer (Fig. 6), or the rotor of a reversible motor, may be connected through suitable gearing to shaft and gear Il (Figs. 1 and 3). This coupling between the dynamometer or motor and the compass gear Il may be effected through ,a flexible shaft (not shown),

thus removing all the control mechanism from the -neighborhood of the compass proper, requiring in addition to the flexible shaft, only a single cable carrying conductors 85, I6, 61.

As described hereinabove in connection with Fig. 1, the trunnions Il of the gimbal ring II are supported in bearings `I8 in the rotatable ring Il. I'he ring IB carries a scale 6B suitably marked or engraved in degrees or compass points on its outer portion and is mounted in a guide ring I! (Fig. 3). In the normal or neutral position of the mechanism the ring I8 and the ring 89 arein predetermined relation to each other; for exy ample, with the north or zero point of the scale 58 opposite the reference line 1i on the ring BI. Ring 69 carries a circular rack I2 which meshes with pinion gear 64 driven by the follow-up motor or. dynamometer. The motor in turning, rotates. the support ring il, the gimbal ring i6 and the bowl 4, causing the scale 6B to remain fixed in azimuth. The heading of the ship is then 4shown by the relationship of the scale i8 to the reference line 'I3 on the plate 1l, which plate is attached tothe binnacle ring 15 xed to the structure of the ship. 1

When the device is to be used for automatic steering, the reversible motor or dynamometer l (Fig. i5)4 is disconnected from shaft 63 and connected through suitable coupling mechanisms, such as a cable 16 illustrated schematically in Fig. 8, to the rudder. The rotation of the followup motor will then apply a pull to the cable li (Fig. 8) which is attached to the rudder quadrant l1, causing the rudder Il to be moved in the proper direction for controlling the direction of movement of the craft. The rudder thus controlled acts to restore the craft and the compass bowl I to its normal or neutral position since the corrective movement is applied to the bowl indirectly through the rudder, the bowl and ship being in fixed relation. The ship or craft being in motion is therefore held to a constant heading or direction.

The mechanism is so designed as to provide for any selection of course to be steered. This selectiorn is effected by manually rotating the compass bowl and the ring Il until the desired course. indicated on scale 6I, is in registry with the reference line 1l. Under this condition, temporarily the float arm 28 is out of alignment with the gap 29, but the follow-up mechanism rapidly restores this arm` to its proper position as above described and, in doing so, brings the ship onto the chosen course, to .which it will be held thereafter by the same mechanism.

In steering a craft which is off course, it is well known that as increasing rudder control is applied to restore the craft to its desired course, the inertia of the craft will cause it to overswing, and when rudder control is applied in the opposite direction to correct this overswing, there will be an overswing in the opposite direction, resulting in a continuous hunting movement of the craft from side to side.

A control system for reducing this hunting to a minimum is shown schematically in Fig. '7. In general, the method comprises the application of heim in an amount proportional to thedeparture, and when the proper amount of helm `has been applied, to reduce it steadily until the rudder is returned to its amidships position. The foregoing cycle is repeated with the helm being applied in decreasing amounts and in the proper direction to the extent required by the departure lunder consideration. By this method the yavring aoaaan of the shipis held to a reasonable minimumand overswing is substantially prevented.

Referring to Fig. '7, the numerals 58 and 59 represent the output terminals of a system similar to that of Fig. 6, i. e., wherein the amplitude, direction, and, phase of the currents, is determined by the relation between the compass and the compass bowl.

These amplified control signals are impressed upon the winding 82 of the dynamometer control relay 80 in series with the winding 98 of a differential relay 81,described hereinafter. Depending upon the position of the member 28 with respect to the members 25 and 28, the dynamometer will operate the contact bar 80 to bridge either the contact 8| or 82 or the contacts 83, 84, it being understood that the other winding 8| of the dynamometer is energized directly from the mains 85 and 89. Assuming that the member 28 is-in such a -position that the contacts 8| and 82 are bridged, then a circuit may be traced from the main 85, contacts 82, 8|, contacts 88, 88 of the differential relay 81, through the winding 19 of the reversible motor 90, adjustable resistance |04, to the other main 89. The relay 81 is preferably designed so that the contact bars |0| and I 05 normally bridge the corresponding fixed contact sets 88-88 and I 084| 01, it being understood that a suitable biasing mechanism such as a light spring or a gravity control may be used for this purpose. The differential relay is provided with two differentially wound coils 91 and 98 which are so designed that theV coil 91 acts to move the contact bars |0|, |05 towards the top only when the energization of the winding 91 exceeds that of the Winding 98. Assuming that the energization of the winding 91 does not exceed that of winding'98, then the winding 19 causes the motor 90 to rotate, for example, in a counter-clockwise direction and thus corre-` spondingly moves the rudder to restore the craft to its proper heading. Suitably coupled to the shaft of motor 90.are brushes 9| and 95, brush 9| having associated therewith a pair of spaced commutator segments 92 and 93, while the brush 95 has associated therewith two resistor sections 94 and 98.

, the cable 18, (Fig. 8), the brushes 9| and 95 are the differential E. M. F. being zero when the,

member 28 is midway between members 25 and 28, and maximum when the said member 28 is wholly covered by one or the other of the members 25 or 28. The current passing through coil 98 is therefore substantially proportional to the departure of the ship 'from' its proper heading. However, as above described, the gradual increase of current through the coil 91 finally causes the said winding to take control of the differential relay and rnove'the bars |0| and |05 towards the top to bridge the contacts 99|00 and |08-|09.

Whenthe lcontacts |08-.|09 are thus bridged, a holding circuit is created for the differential relay, this circuit being traceable from the main 85, brush 9|, segment 92, contacts |08, |09, holding coil H0, back to the main 89, The armature Thus, as the motor 90 rotates to control the rudder, for example, by means ofv .main 89. g l

As the motor turns to apply 4ruddervit moves brush' 95 on to resistance 94 and as thisresist- |05 is thereby held in its upper position, main'- taining closed the gap between contacts |08 and |09. In parallel with the holding coil I|0 is a heating coil for the thermostatic time delay switch |I2.

When winding 81 overcomes'winding 98 and armature |05 is lifted into contact with contacts |08, |09, the circuit between contacts 88 and 98 is broken and current ceases to flow to the winding 19 of the motor 90, which thereupon slows down and stops. `At this stage a predetermined amount of rudder has been applied, but the ship is still off her course. For a short time interval, until the current passing through the heating coil causes the contact bar I4 to close the gaps I i5, H8, the rudder remains in the on position. thereby checking the yaw or causing the vessel to commence its movement back to its course. Upon this gap IIS-H8 being closed, current is enabled to flow from contact |09 to contact H5, thence` through contact bar ||4 to contact H8, to winding ||1 of the motor 90, to adjustable resistance |04, back to the main 89.

The motor now rotates in the opposite directionl to that due to the energization of winding 19, and as a result the rudder is moved back towards its amidships position. When this position is attained the brush 9| registers with the gap H8, breaking the circuit to the holding coil H0. The circuits to the thermostatic winding III and to the motor winding ||1 are also broken with the result that the motor stops. Armature |05falls away from contacts |08, |09 and armature i 0| bridges the gap 88, 88.

'I'his completes a cycle of operations, the effect of which is to check the yaw of the vessel. but not necessarily to bring it back exactly to its course coincidentally with the return of the rudder to its amidships position. Normally, after completing this cycle, the heading of the ship will be closer to the proper course than at the commencement of the cycle, but there will still be a small departure in the same directionV as at the start. If this should be the case the contacts 8| and 82 will still b e bridged by the armature and currentwill again flow to winding 19 of the motor applying rudder in the same direction as the v,previous cycle.` The amount of departure of thefship from its course now vbeing small., the differential E; M. F. between members 25 and `remainder of the cycle is repeatedas before and this time it is probable that the vessel is so close to its course that the differential E. M. F. generated between plates 25 and 28, after ampliflcar tion, will be insufficient to move the armature 80 far enough away from its neutral position to bridge either of the gaps 8|92 or 83-94.

When the vessel departs from the course in the opposite direction enough to cause contact bar 80 to bridge the gap 83-84, current is enabled to flow from the main to contact 84, through contact bar 80 to contact 83, thence to contact |08, through armature |05 to contact |01, to motor winding ||1, resistance |04, and back to the ance diminishes the ow of current through the winding 31 of the differential relay 01 is increased. When the energization of this winding exceeds that of winding 00, the armature closes the gap between contacts 90 and |004 and armature opens the gap between contacts |00 .and |01. The opening of the latter gap breaks the circuit to the motor winding |1 so that the motor stops.

Current flows from main 95 through brush 9| and conductor segment 93 tc the contact |00, amature |0|, and contact 99. From contact 99 there are three branches leading back to main 09.

The first branch energizes the holding coil |I9 and maintains the armature |0| in contact with contacts 99 and |00; the second branch energizes the heating coil |20 of the thermostatic switch |24, which after a predetermined short time interval causes member |2| to bridge the gap between contacts |22 and |23; the third branch provides a circuit from contact 99, to contact |22, contact bar |2|, contact |23 to motor winding 19 and thence by resistance |04 back to main 89.

The motor is thus rotated in the opposite direction and acts to return the rudder to the amidships position; it also moves the brush over the segment 93 towards the gap ||9. Upon this gap being reached the circuit is broken, the holding coil ||9 is released and the motor stops, again completing a cycle. l

In automatic steering systems it is important that at any time, for example in emergency, the automatic system may be cut out instantly and completelyl and full manual control restored to the helmsman. A method of accomplishing this is shown in Figs. 9 and 10, in which the numeral |30 designates a wheel for hand steering.` This wheel rotates about the shaft |3 I. and carries the sprocket |32 which engages the chain |33 of sufiicient length to permit of putting the rudder over to its limiting position. 'I'he ends of this chain are attached to cables |34, |35, which are led over suitable pulleys (not shown) to the location of the steering motor 90. y This motor, through suitable reduction gearing, drives the shaft |39. On shaft |39 are loosely mounted the two sprockets |31, |30, which are pinned together and to the disc |39 by the studs |40. Engaging the teeth of one of these sprockets is the chain |42, and engaging the teeth of the other sprocket is the chain |43. The ends of chain |42 are attached to the free ends of the cables |34 and |35 leading to the hand steering wheel, while the ends of chain |43 are attached to cable 19 which in turn is attached to the rudderquadrant 11. It is apparent that with the sprockets |31 and |39. fixed together and idling on shaft |39, the wheel |30 moves the quadrant and the rudder in the manner customary with hand steering, without any interference whatever from the presence of the automatic mechanism.

Keyed to shaft |39 of motor 90 is the plate |44 on which are-mounted the electromagnets |45 and |49. The disc |39 is of iron or other suitable magnetic material. When the electromagnets |45, |49 are energizedtherefore, they exert an attraction for .the iron of disc |39 and draw this disc towards the plate |44 which carries a facing |41 of cork or other friction material. As a result disc |39 and sprockets |31 and |30 are temporarily locked to the plate |44 and shaft |39, and are caused to rotate when the motor rotates, thereby moving the rudder in accordance with the automatic signals impressed upon the motor circuit and incidentally turning the hand wheel |30.

to the steering wheel |30.

The manual switch |40 is located in proximity When this switch is closed current is permitted to flow from the mains 00, 09, through conductors |49, |50 to the windings of the electromagnets |45, |49, energizing these windings and bringing into operationthe automatic steering system. The opening of this switch cuts out the automatic system and restores the wheel |30 to use for hand steering. It will be understood, of course, that any suit-able form of clutch may be employed to bring together the fixed and free units on shaft |39, for example, the friction-clutch may be replacedl by a dog clutch, and operation may be by Bowden wire or cable. manually controlled from the steering wheel position.

The response of a craft to the action of its rudder varies for a number of reasons, depending on the size of the rudder. the speed of the craft, the inertia of the craft, and the effect oi weather and sea conditions. It is necessary to provide means for giving a correct initial setting to the amount of rudder applied for given departures of the craft from the course, and it is also desirable, in certain cases, to provide means for changing the rudder response under changing sea and Weather conditions. In the present invention three adjustments are provided in the variable resistances 99, |04 and ||3.

Resistance 99l is in circuit with coil 91, so-that by adjustment of 99l the amount of angular movement of brush 95 necessary to overcome coil 98 may be increased or decreased. Thus the amount of helm for a given departure from the selected course may readily be adjusted. Normally, this resistance will be set at a suitable value, found by trial and error, and will be fixed there, although provision may be made to change the resistance to apply more or less rudder for a given departure if and when this should be considered desirable.

Resistance I I3 controls the period of time during which the rudder remains in the on position, an increase in the resistance delaying the heating of the thermostatic windings and |20 and thus delaying the closing of the circuit for operating the motor to remove rudder. This also is normally set as a matter of initial adjustment, and then fixed in the set position. but as in the case of resistance 99", manual means may be provided for adjustment to weather conditions, should this be desired.

In the case of large crafts, the amount of hunting may be reduced by applying the corrective rudder more slowly as the amount of helm is increased. For example. from its amidships position of the rudder during its initial movement, the rate may be predetermined, and then as more and more helm is applied, the rate of application of the rudder may be slowed down. This may be accomplished by employing a variable speed motor. Thus the motor 90 may be of the variable speed type and the reistance |04 may be designed so that as the motor begins to rotate, this resistance has a relatively low value. As the motor continues to rotate. the amount of series resistance |04 may be correspondingly automatically increased, thus reducing the E. M. F. at the motor coils and correspondingly reducing the speed of the motor and application of the rudder. A method o! accomplihing this is schematically illustrated in Fig. 1l. In Fig. 11 the shaft carrying brushes 0| and 95 is provided with an additional brush |25. The support for the commutator segments 92, 03 and resistance both during its on and during its oif.' motion,

whereas with the arrangement of Fig. 11, the rate of application of rudder is controlled by resistance |04 only during the on movement of the rudder.

While the invention has been described above with reference to a ship, vessel, or craft, it is understood that these are merely yillustrative elds of application. For example, the invention may be used on any kind of moving vehicle whose direction or orientation with respect to a selected heading may be gauged and/or automatically controlled. The term departure control, there'- fore, as employed in the specification and claims, refers to any type o2 system wherein the position of one member is to be controlled with re` spect to another member. Similarly, the term overlapping as employed'herein to describe the relation between members 25 26 and .28, is intended to cover not only a physical overlap, but any other equivalent overlap. For example, the gap 29 may be wider than the member 28, so long as relative movement between member 28 and members 25, 26 results in the induction oi corresponding E. M. F.s. Similarly, instead of dis-` posing members 25, 2wadjacent each other, they may be disposed on opposite diameters and the compass float "may be provided with a pair of -diametrically disposed collector members to induce corresponding E. M. F.s on the fixed members.

What I claim is:- 1. The method of steering which comprises creating an E. M. F. proportional to the departure of a craft from a chosen heading, creating a second E. M. F. proportional to the departure of the rudder from its neutral positionapplying rudder until said second E. M. F. bears a predetermined magnitude relation to said first E. M. F., and then restoring said rudder directly to its neutral position.

2. In automatic steering apparatus, a compass,

a rudder means for selecting the direction of rudder application to correct for the departure of a. craft from its course in accordance with the direction of said departure, differentially balanced means responsive to the movements oi said compass and said rudder for regulating the application of said rudder in an amount proportional to said departure, and means for steadilyy removing said rudder application independently of said balancing means.

3. Automatic steering mechanism comprising` means for selectingthe direction of rudder application, means forapplying said rudder, means for creating an E. M. F. proportional to the departure of a craft from its chosen heading, means for creating a second E. M. F. proportional to the movement of said rudder-applying means from a predeterminedneutral position, means for comparing said E. M. F.s to stop said rudder applying means and to restore the rudder-applying means to neutral position.

4. In a system for controlling a steering member or the like, a source of steering control currents proportionate to the extent to which said membervis to be moved, a motor for moving said member, a motor control relay, a member driven by said motor for producing another current independent oi the control current, means for diierehtialiy applying said currents to said conf trol relay, means controlled by said relay for 'l stopping the steering member at a position determined by said control currents, and means effecf tive after the stopping of the steering member for automatically reversing the direction of move- -ment of said member until said member resumes its neutral position.

5. In a system for controlling a steering rudder or the like, means for producing steering control current corresponding to the extent to'which said rudder is to'be moved, a device responsive to the polarity of said `current, a motor for moving saidy rudder, means controlled by said motor for producing another current whose instantaneous amplitude corresponds to the off-neutral position of said rudder, means responsive to a predetermined amplitude relation between said two .cur-

rents to effect stopping of said rudder, and means automatically effective upon stopping of saidl rudder to restore said rudder to neutral position.

6. In asystem'for controlling a steering rudder or the like, means for creating an E. M. F. proportionate to the extent to which said rudder is to be moved away from neutral position, means forcreating another .lil1 M. F. varying instantaneously in accordance with the position of said rudder from neutral, mrans for continuing the off-neutral movement of said rudder until said currents bearfa predetermined magnitude relation, and means automatically responsive to the attainment of said relation for causing said rudder to move back to its neutral position.

'7. In a system for controlling a steering rudder or the like, means for creating an E. M. Fl proportionate to the extent to which said rudderis to be moved away from neutral position, means for creating-'another E. M. F. varying instantaneously in accordance with the position of saidrudder from neutral, means for continuing the oifneutral movement of said rudder until said currents bear'a predetermined magnitude relation, means automatically 'responsive to the attain-l ment of said rf-lation for causing said rudder to move back to its neutral position, and means for causing the foregoing operations tobe repeated in successively decreasing rudder movements.

8. In a departure-control system, a steering rudder or the like, al source of steering control der or the like, a source of steering control current, a motor for said rudder, means controlled bysaid motor for producing another current, a diii'erential device controlled by both said currents, a time delay device controlled by said differential device, the supply of current to said motor for applying said rudder being controlled by said diierential device, and the supply of current to said motor for removing said rudderv being controlled by said time-delay device.

10. In a system for controlling a steering rudder or the like, a motor for operating the rudder;

a source of steering control E. M. F., a polarized relay device controlled-by said E. M. F., means controlled by said motor for producing another E. M. F., a device controlled differentially by said `E. M. F.s, a time delay device controlled by said differentially controlled device, and a control circuit for said motor, adapted to .start said motor under control of said polarized relay device, to stop said motor under control of said differentially controlled device, to reverse said motor under control o! said .time delay device and to ilnally stop said motor under control of said motor controlled means.

l1. In a departure control system, a rudder or similar steering mechanism, compass controlled means for oscillating therudder between neutral and an angular position determined by said departure, means for controlling the amplitude and rate, oi' oscillation of the rudder, and means for independently controlling the period during which the rudder remains in its maximum off neutral position prior to being restored to neutral position.

12. In combination, a steering device, a directional indicator, means to produce an E. M. F. dependent upon the position oi said indicator, a ilrst selector device dependent upon the polarity of said E. M. F., a second selector device dependent upon the magnitude of said E. M. F., areversible motor, circuit arrangements eilective with said first selector device in one condition to eilect clockwise rotation of said motor and in another condition to effect counterclockwise rotation of said motor, a commutator controlled by said motor, a 'source of E. M. F., controlled by said commutator, and means for balancing said commutator controlled E. M. F. against said directional controlled E. M. F. to change the condition of said second selector device to reverse the direction of rotation of said motor. A

13. In combination, a steering device, a source of directional control signals, a relay controlled by said signals, a two position switch controlled by said relayl a reversible motor, circuit arrangements ciiective with said switch in one position to control clockwise rotation of said motor and eifective in another position to control counterclockwise rotation of said motor, a commutator controlled by said motor, ditierential windings for said switch one of said windings being energized from said source of control signals and the other winding being energized under control oi said commutator, and a holding circuit for said relay including said cornmutator, said commutator arrange to break said holding circuit when the steering device is in a preselected neutral position.

14. In a departure control system, a rudder or similar steering member, compass controlled means ior automatically moving said rudder oil.- neutral to a predetermined extent and in a predetermined direction to correct for a given de.

parture, means for returning said rudder to its neutral position prior to4 complete correction of said departure, and means for delaying the commencement of said return movement of said rudder substantially independent of the period during which said rudder is moved to its ofi-neutral position.

i5. In a departure control system, a rudder or similar steering member, compass controlled meansfor automatically moving said rudder to a predetermined extent and in a predetermined direction to correct for a given departure, means i'or restoring said rudder to its neutral position substantially independently oi' the compass indicatlon, and a variable impedance for adjusting the extent oi rudder movement.

16. In a departure control system, a rudder or similar steering member. compass controlled means for automatically moving said rudder to a predetermined extent and in a predetermined direction to correct for a given departure, means for progressively decreasing the rate of movement oi said rudder as the latter departs from its neutral position, and means for restoring said rudder to its neutral position.

17. In a departure control system. a rudder or similar steering mechanism, compass controlled means for oscillating the rudder between neutral and an angular position variable according to said departure, and means substantially independent of the particular angular position to which the rudder is moved for controlling ths period during which the rudder remains in said angular position prior to being restored to neutral position.

18. In a departure control system, a rudder or similar steering mechanism, compass controlled means for oscillating the rudder between neutral and an angular position variable according to said departure, means substantially independent of the particular angular position to which the rudder is moved for controlling the amplitude of the rudder oscillations, and means for controlling the period during which the rudder remains in said angular position prior to being restored to neutral position.`

19. In a departure control system, a rudder or similar steering member, electromagnetic means for oscillating the rudder in a recurrent manner between neutral and an angular position determined by said departure, compass controlled means i'or reversibly energizing said electromagnetic means, 4and means for controlling the amplitude and rate oi oscillation of the rudder.

20. In a departure control system, a steering rudder or the like, means for generating steering control currents, electromagnetic means for causing said rudder to oscillate between a preselected neutral position and an olf-neutral position determined by and in proportion to the departure and then between said oit-neutral position and the neutral position, and means for applying said control currents to reversibly energize said electromagnetic means to cause said oscillations to continue until the required amount of steering has been effected.

21. A system according to claim 20 in which the said oscillations are repeated with decreasing amplitude to effect the required amount oi steering.

22. A system according to claim 20 in which means are provided for controlling the amplitude of the rudder oscillations in accordance with the extent of steering required and also in accordance with weather conditions and the like.

23. In'a departure control system, a rudder or similar steering member, electromagnetic means for actuating said rudder, compass controlled means for reversibly energizing said electromagnetic means to move said rudder to an extent and in a direction determined by said compass and in proportion to the extent of departure to correct for said departure and for automatically and positively restoring said rudder to its neutral position prior to complete correction of said departure. and means for causing the rudder to repeat the foregoing cycle until the departure is oompletely corrected.

24. 1n a departure control system, a directional indicator, a rudder or similar steering member, electromagnetic means for actuating said rudder,

means controlled by the movements of said indicator and said rudder for reversibly energizing said electromagnetic means for automatically moving said rudder to an extent and in a direction determined by said indicator to correct for a given departure, for automatically and positively restoring said rudder to its neutral position prior to complete correction of said departure, and for causing the rudder to repeat the foregoing cycle until the departure is completely corrected.

25. In a departure control system, a directional indicator, a rudder, electromagnetic actuating means for said rudder, means for creating currents corresponding to the indications of said indicator, meansfor Ycreating currents corresponding to the position of said rudder, and control means dependent upon said currents for reversibly energizing said electromagnetic means for moving said rudder in a direction and to an extent determined by said indicator to correct for a given departure, for restoring said rudder to its neutral position prior to complete correction of said departure, and for causing said rudder to repeat the foregoing cycle until the departure is completely corrected.

26. In a departure control system, a compass, a rudder or similar steering member, electromagnetic means for moving said rudder, compass controlled means for energizing said electromagnetic means to move said rudder to an extent and in a direction determined by said compass to cor-- rect for a given departure, and means effective when said rudder has been moved 'to said extent for reversibly energizing said electromagnetic means to return said rudder to its neutral position substantially independently of the compass indication.

HUMPHREY F. PARKER. 2o 

